1. Field of the Invention
The invention relates to cap retaining devices and particularly to a device for connecting the cap of a pressure/temperature test plug with the plug so that the cap is not lost when measurements are taken at the valve.
2. Description of the Prior Art
In high pressure heating and cooling systems, it is necessary to routinely perform numerous temperature and pressure tests at various points in the system in order to insure the proper and economical operation of the system. In small systems, temperature and pressure gauges are often permanently installed in the pressure lines at several points in the system. However, in large systems, it is both impractical and cost-inefficient to install gauges at all the necessary points in the system, which can often total as many as 700 to 800 points. Accordingly, most large systems employ test plugs at the necessary test locations throughout the system in order to allow measurements to be made at all of those points. The test plugs are normally closed valves which allow a temperature or pressure probe to be inserted in the line and measurements taken.
U.S. Pat. No. 3,797,317 which is incorporated herein by reference reveals a test plug of the type described. As seen therein, the test plug is inserted into a threaded opening in a pressure line. The plug includes a closure cap which assists the internal valving mechanism in sealing the test plug against leakage when measurements are not being made.
One of the problems associated with the prior art devices is that the closure cap, once removed during the measurement process, is often lost or misplaced.
Numerous devices are known in the art for retaining a cap removed from an opening. An example is U.S. Pat. No. 1,021,203 which discloses a closure for vacuum service inlets having a chain 20 extending between a closure cap 14 and a nipple 1 to prevent the cap 14 from being lost when it is removed from the nipple 1.
U.S. Pat. No. 2,172,311 reveals a valved tap plug having a chain 39 which prevents the plug 34 from being separated from a plug body 12.